Those portable "no parking" signs outside of apartment buildings in New York City are merely suggestive. It's actually illegal to prevent anyone from parking on a public street, though try telling that to the doorman repelling your rusty Escort.

The typically metal-rimmed "No Parking" or "No Blocking This Entrance" signs carry no legal weight, even if they typically serve the residents of the buildings and make it easier for them to access transportation. When a reporter for The New York Times attempted to test the limits of legal parking she was met with a mix of guilt, diplomacy, and expletives.